Last week the Seattle area became unseasonably cold. During the past three years that the 7-Oh-Fun has been flying we had not seen temps in the 20s.

Disclaimer: No warranty is implied and no liability is accepted. This sort of preheater will require supervision. Do not leave unattended.

What to do? If necessity is the mother of invention, then the Lowe's next to the airport was the father.

I found  the following cheap items:

  • UtiliTech Cermamic Electric Space Heater ($25 electric heater, Item #485219)
  • Plastic vent ($5, Item #328910)
  • Flexible vent tubing ($10, Item #40529)
  • Aluminum tape ($5, Item #433282)
  • Tube spring clamps ($2, Item #55597) 

Here are all the parts before assembly:

After unpacking the parts I took the aluminum tape and masked off the sides of the heater to prepare for the vent being attached.

I then removed the louvers from the vent and taped it with the aluminum tape over the heater with the round tube adapter pointing out.

Finally I used the clamp to attach the tubing. Towels were used to plug the front of the cowling. The free end of the tubing was inserted into the lower rear area of the cowling. The oscillation feature of the heater was turned off. 

You can also see that I used a VERY low powered hairdryer pointed at the oil tank to assist.

The heater was adjusted to be "not too hot" with the fan on high. The whole system took my oil and engine from 24F to 48F in about 30 minutes.

Good luck!

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Comment by John Austin on December 21, 2013 at 11:36am

Just one word of caution on all pre-heaters adapted from room electric heaters, hair dryers, etc. I had a cousin who was an engineer specializing in custom industrial air management. He told me that all the common residential heaters and blow dryers' fans and motors are not designed to "push" air against resistance from ducting not in the original design. Therefore, be very cautious in the length and diameter of your flexible ducting so as not to create too much resistance. I would not recommend running a home-made design unattended unless it has been thoroughly tested.

By the way, those "Hornet" aircraft heaters are excellent, safe, and pricey! I bought an identical heater from them for an "enclosure" rather than an aircraft and it was less expensive. However, they seem to be coming out with new models all the time.


Comment by Louis W. Ott on December 15, 2013 at 1:41pm

I use one of these heat pads on the bottom of my Corvair oil sump. It warms the entire engine after a while. Either control by thermostat or leave it on all the time when its cold out.

Comment by Jesse Hartman on December 13, 2013 at 3:33pm

So I just looked at the ACS heater for the rotax....... 400.00   WTF are you kidding me.

Comment by Dan Stanton on December 13, 2013 at 3:15pm

Oh, ;ther box on the floor is a milkhouse thermostat, stick it under the cowel

Comment by Dan Stanton on December 13, 2013 at 3:13pm

I have been using this setup for several years without any problems. IO360. VW Viking.

It woarks very well. It is turned on right now for dounuts in the morning.



Comment by Dan Stanton on December 13, 2013 at 3:11pm

Comment by Bob McDonald on December 13, 2013 at 6:14am

Its -20C here these days. Even if you insulated the delivery hose your ability to heat the engine is reduced to ineffective. Remember the colder the air is outside the less "hot" the heater will be able to raise the inlet air. Break the Bank and buy a Rieff ROTAX 912 heater from Aircraft Spruce. It is a 100 watt element epoxied to bottom of engine block, and a 50 watt heater in a gear clamp style around the oil tank. Oil tank element is supervised by a thermostat to prevent over heating...NO Fire hazard. Simply plug in as you would a car engine. At -10F my engine oil is 60 degrees on start up. You can damage a Rotax engine by not preheating it correctly.

Comment by Jesse Hartman on December 13, 2013 at 6:09am

My wife starts her car up at 0 F and just goes.  200k on that engine.

Comment by Bob Pustell on December 12, 2013 at 9:32pm

I would speculate that the core of your engine was still stone cold. It takes a long period of heating to get the crank and central sections of the case up to temp. The "short but sweet" method of pre-heating gets the oil and cylinders warm enough that the engine will start, but the heart of the engine is still stone cold. At that heart is where problems can happen -- when very cold an aluminum engine case with a steel crank can cool to zero bearing clearance due to different expansion/contraction rates of the two metals. Everything needs to be up to temp before start if long term damage is to be avoided. At the fairly moderate temps you describe I doubt you had problems. At the considerably cooler temps we get here in NH (6 degrees F and dropping tonight) you can damage your engine without an hours long pre-heat.

Comment by Tim Garrett on December 12, 2013 at 5:27pm
That's great John! Makes me want to try it. Might need a second one ducted to my coat while I wait.:)

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